Discriminant analysis and column name in the code - r

Question

I have been writing a code to ease performing a discriminant analysis using the lda function. But actually I have a step which I cannot solve. And it is when I have to introduce the name of the categorical column in the code. Imagine we have the next table (called smoke), in which the column Factor represents the groups (in our cases, smoker and nsmok).
smoke
Factor Lung Heart Blood
1 smoker 7 22 15
2 smoker 8 21 12
3 nsmok 22 9 5
This is the code I have been preparing. Please, look at the XXXX's in the code (it appears twice). I want them to write automatically the name of the categorical column, instead of writing directly it twice.
lda=lda(XXXX~.,data=Smoke)
plot(lda)
lda
lda$counts
lda$svd
lda.p=predict(lda)
Tabla=table(Smoke$XXXX,lda.p$class)
Tabla
diag(prop.table(Tabla, 1))
sum(diag(prop.table(Tabla)))
I thought that writing...
colnames(Table)[1]
... would solve it. But actually there still exist some errors when running the code.
Otherwise, I though that introducing directly the name in this way:
Column_Factor-> Factor
and writing Column_Factor in the two places in the code would solve it. But it isn't.
Any ideas?

Answer 1

You could do something like this:
library(MASS)
#gets the column name of the factor, maybe check if there is only one factor column first
Column_Factor <- names(Smoke)[sapply(Smoke, class)=="factor"]
#creates the formula by pasting the name and the RHS
lda <- lda(as.formula(paste(Column_Factor,"~.",sep="")),data=Smoke)
plot(lda)
lda
lda$counts
lda$svd
lda.p=predict(lda)
#selects the column using the variable
Tabla=table(Smoke[,Column_Factor],lda.p$class)
Tabla
diag(prop.table(Tabla, 1))
sum(diag(prop.table(Tabla)))